Need help adding color to FONT AWESOME icons

Can anyone tell me how to add color to font awesome in HTML? 

EXAMPLE:

<span class="fa-stack fa-lg">
  <i class="fa fa-square-o fa-stack-2x"></i>
  <i class="fa fa-twitter fa-stack-1x"></i>
</span>
fa-twitter on fa-square-o<br>

Little un sure how to add color

With CSS:

.fa-twitter {
	color: #38A1F3;
}

Inline:

<i class="fa fa-twitter" style="color:#38A1F3;"></i>